1. Field of the Invention
The present invention relates to a package for a semiconductor device (hereinafter called PKG), particularly relates to PKG having a radiating substrate provided with a chip mounting part for directly mounting a semiconductor chip (hereinafter called a chip).
2. Description of the Related Art
Heretofore, this type of PKG has been formed by brazing a ceramic side wall for airtightly sealing a chip directly mounted on a chip mounting part of a radiating substrate.
FIG. 8 is a schematic plan showing a PKG of related art and FIG. 9 is a schematic sectional view when viewed along a line A8-A8xe2x80x2 in FIG. 8. FIG. 10 is a partial sectional view showing a part equivalent to the position of a line C8-C8xe2x80x2 in FIG. 8 when a semiconductor device using this PKG is mounted on a radiator fin of an amplifier and others.
Referring to FIGS. 8 to 10, as for this type of PKG 80, a concave portion 86 is provided on each opposite side 88, 89 in a first direction of a radiating substrate 81, for fixing the radiating substrate 81 on a radiator fin 100 by a screw 13. A chip mounting part 82 is provided in the approximately center of the radiating substrate 81 for directly mounting a chip 820. The periphery of the chip mounting part 82 is surrounded by a ceramic side wall 83 brazed on the radiating substrate 81. External leads 87 are led out from the side ends of the radiation substrate 81 in a direction perpendicular to the first direction.
For the semiconductor device, after the chip 820 is mounted on the radiation substrate 81, the chip 820 and a part extended inside the ceramic side wall of the external lead 87 are bonded via a gold wire for example and the upper part of the side wall is airtightly sealed with a ceramic cover 90 for example.
The PKG 80 of the related art is formed by brazing and plating the radiating substrate 81 and the ceramic side wall 83. That is, as materials different in a coefficient of thermal expansion of the radiating substrate 81 made of metal and the ceramic side wall 83 are heated and bonded, convex warpage 91 of a few tens micrometer is formed on the lower side of the radiating substrate 81 as shown in FIG. 9.
Therefore, when the semiconductor device using the conventional type PKG 80 is fixed on the radiator fin 100 by the screw 13 as shown in FIG. 10, stress that levels the warpage 91 on the back is generated. There is a problem that at this time, superficial stress becomes maximum on the boundary of bonding 92 between the ceramic side wall 83 on the surface and the radiating substrate 81 and a crack 93 of the ceramic side wall 83 and an interface crack 94 between the ceramic side wall 83 and the radiating substrate 81 are easily made around the boundary.
A package according to the present invention includes a radiating substrate, a concave portion for a screw formed on a first side of the radiating substrate, a first groove formed on the first surface between a chip mounting portion and the concave portion of the radiating substrate, and a second groove on a second surface of the radiating substrate opposite to said first surface. Therefore, no crack is made on the ceramic side wall or on the boundary of bonding between the ceramic side wall and the radiating substrate when the PKG is mounted on a radiator fin of an amplifier and others using a screw.